fall back to local library file if download fails

DidYouKnowWidget.cc

@@ -66,7 +66,7 @@ void DidYouKnowWidget::updateTips()
 {
     // Number of seconds after which the local tips library is considered outdated
     const int outdatedSeconds = 1 * 24 * 60 * 60;
-    const QUrl libraryURL("https://graphics.rwth-aachen.de:9000/Staff/TipOfTheDayLibrary/raw/master/tips.json");
+    const QUrl libraryURL("https://graphics.rwth-aachen.de:9000/born/Plugin-DidYouKnow/raw/master/Library/tips.json");
 
     // Check for existing local library file
     QFileInfo libraryFileInfo(libraryFileName());
@@ -101,9 +101,14 @@ void DidYouKnowWidget::updateTips()
 
     mTips.clear();
     QFile libraryFile(libraryFileName());
+    if (!libraryFile.open(QIODevice::ReadOnly)) {
+        // Try library file from local repository as fallback
+        std::cout << "Could not open " << libraryFile.fileName().toStdString() << ". Falling back to local library." << std::endl;
+        libraryFile.setFileName(":Plugin-DidYouKnow/Library/tips.json");
         if (!libraryFile.open(QIODevice::ReadOnly)) {
             throw ConfigError("Could not open " + libraryFile.fileName().toStdString());
         }
+    }
     QByteArray libraryData = libraryFile.readAll();
     QJsonDocument libraryDoc = QJsonDocument::fromJson(libraryData);
     if (!libraryDoc.isObject()) {

resources.qrc

+<RCC>
+  <qresource prefix="Plugin-DidYouKnow">
+    <file>Library/tips.json</file>
+  </qresource>
+</RCC>